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What is the Formation of Becke Line?
What is the Formation of Becke Line?
The Becke Line appears when a glass particle is mounted in an oil with the same refractive index.
The Becke Line appears when a glass particle is mounted in an oil with the same refractive index.
False
What does the Becke Line represent?
What does the Becke Line represent?
A visible halo of light formed around a glass particle in oil.
What happens to the Becke Line when the higher refractive index material is focused on?
What happens to the Becke Line when the higher refractive index material is focused on?
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What is required to see contrast under the microscope?
What is required to see contrast under the microscope?
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What is the purpose of Cargille Liquids in the Becke Line test?
What is the purpose of Cargille Liquids in the Becke Line test?
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If the Becke Line moves into the glass, what can be inferred about the refractive index of the glass?
If the Becke Line moves into the glass, what can be inferred about the refractive index of the glass?
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What should you do after determining a rough range of the glass's refractive index?
What should you do after determining a rough range of the glass's refractive index?
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Study Notes
Formation of Becke Line
- Becke Line formation occurs at the interface of two materials with different refractive indices: a particle and the mounting oil.
Refraction of Light
- Light refraction occurs when passing through materials of different refractive indices, causing light to bend around object edges.
- The direction of bending depends on which material has the higher refractive index, resulting in a visible halo called the Becke Line.
Observations with Becke Line
- When focusing on glass with a higher refractive index, the Becke Line appears to move towards the glass as the stage is lowered.
- A decrease in Becke Line size indicates movement towards the particle, while in the case where oil has a higher refractive index, the Becke Line appears to move towards the oil.
Key Rule for Observing Becke Line
- The Becke Line always moves towards the material with the higher refractive index when focusing on the edge and lowering the stage.
Importance of Refraction in Imaging
- Contrast under the microscope is achieved by light passing through and being scattered by the sample, with the objective lens focusing these rays for interference.
Visibility Conditions
- When a glass particle has the same refractive index as the surrounding liquid, it appears invisible under the microscope, assuming there is no color differentiation.
Application of Becke Line Test
- The darker edge represents the glass particle, and the bright halo is the Becke Line. Observing the movement of this halo can indicate which material has a higher refractive index.
Methodology for Becke Line Testing
- Starting with known refractive index oils (Cargille Liquids), the glass is mounted, and the Becke Line test is performed.
- If the Becke Line moves towards the glass while using an oil of 1.500 R.I., it indicates the glass refractive index is greater than 1.500.
Determining Glass Refractive Index Range
- If the Becke Line moves towards an oil with a higher R.I. (1.600), the glass R.I. will be between 1.500 and 1.600, guiding further tests.
Refining the Refractive Index Measurement
- Subsequent tests with intermediate oils (e.g., 1.550 R.I.) help narrow down the exact refractive index until the glass disappears in an oil of equal refractive index.
Becke Line Method Steps
- Use medium to high power magnification during observation.
- Observe the Becke Line movement by closing the aperture diaphragm and lowering the stage to confirm the higher R.I. material.
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Description
Explore the concept of the Becke Line through these flashcards. Learn how the refractive index of a glass particle interacts with a mounting oil, affecting light refraction. This quiz is essential for understanding optical mineralogy.
